1. Field of the Invention
The invention relates to solid oxide fuel cells and in particular to the type of cells with the electrode material supported on a metallic support material.
2. Description of the Related Art
Recent development of thin supported electrolytes in connection with improved electrode performance allows lowering the operation temperature to temperatures where strong, cheap and ductile metallic materials may be used for bipolar separation plates between the cells. Current intermediate temperature solid oxide fuel cells operate at temperature from about 500° C. to 850° C., whereas older types of fuel cells operate at 900° C. to 1000° C. The lower operation temperature makes it possible to use metallic materials for the cell component supporting the electrode layers as well as the thin electrolyte layer.
In the known solid oxide fuel cells the layer supporting the electrochemical active element is a porous structure made of metallic or ceramic materials or mixtures of metallic and ceramic materials. Metallic felt or plasma sprayed porous layers have been proposed as the supporting structure, in which the pores in the support layer distribute the cell reactant gases.
U.S. Pat. No. 6,048,636 discloses an electrode for a fuel cell with a porous, mechanically strong, self-supporting layer consisting of a cermet comprising Al2O3 or TiO2 to which nickel is admixed. By locating gas channels within the mechanically stabilising electrode layer, the gas can be supplied to a catalytically active layer by a shorter path as compared to prior art.
U.S. Patent Application Publ. No. 2002/0004155 discloses an etched interconnect for fuel cell elements comprising solid oxide electrolyte, an anode, and a cathode and includes a conductive base sheet having first and second faces having anode and cathode gas flow passages, respectively. These gas flow passages can have various geometries selected to optimise fuel and oxidant gas flow and they can be prepared using a photochemical etching process. When in use, the interconnect is placed between two fuel cells. The interconnect surface corresponds to the surface occupied by a single fuel cell.
The proposed porous cell support materials are, however, problematic with respect to manufacturing methods, and porous materials posses poor mechanical properties. Furthermore, a porous gas distribution body does not permit the flow pattern of the cell reactant gasses to be controlled.
It is the objective of this invention to provide a fuel cell whose supporting structure for the electrochemically active element is made of a metallic body perforated with fine holes or channels in a controlled pattern to enable a controlled distribution of the reaction gasses directly to the electrochemically active element.